There are cases where contact with a customer is recorded and the recorded content is analyzed and utilized for, for example, customer care and product development thereafter. Although there have already been such cases, attention has been drawn to analysis and utilization of documents in which all exchanges of communications between customers and call centers that accept inquiries about products from the customers are recorded (texts including all inquiries, interim status, and final responses and hereinafter referred to as the conversation history document) as an example of utilization of big data. For example, the above-mentioned call centers use past conversation history documents when finding an appropriate solution for a new inquiry.